Composite aerogel material that contains fibres

ABSTRACT

The present invention relates to a composite material that contains 5 to 97%-vol aerogel particles, at least one binder, and at least one fibre material, the diameter of the aerogel particles being ≧0.5 mm, a process for manufacturing this, and the use thereof.

[0001] The present invention relates to a composite material thatcontains 5 to 97%-vol of aerogel particles, at least one binder, and atleast one fibre material, the diameter of the aerogel particles being≧0.5 mm, a process for manufacturing this, and the use thereof.

[0002] Because of their very low density, great porosity, and small porediameters, aerogels, in particular those with a porosity of over 60% anddensities of less than 0.4 g/cm3, display an extremely low thermalconductivity and for this reason are used as thermal insulationmaterials, as described in EP-A-O 171 722, for example.

[0003] However, their high level of porosity leads to a low mechanicalstability, both of the gel from which the aerogel is dried, and of thedried aerogel itself.

[0004] In the broadest sense, i e., when regarded as “gels with air asthe dispersant,” aerogels are manufactured by drying a suitable gel.When used in this sense, the term “aerogel” includes aerogels in thenarrower sense, such as xerogels and cryogels. A gel is designated as anaerogel in the narrower sense if the liquid is removed from the gel attemperatures above the critical temperature and starting from pressuresthat are above the critical pressure. In contrast to this, if the liquidis removed from the gel sub-critically, for example with the formationof a liquid-vapour boundary phase, then the resulting gel is, in manyinstances, referred to as xerogel. It should be noted that the gelsaccording to the present invention are aerogels in the sense that theyare gels with air as the dispersant.

[0005] The process that shapes the aerogel is concluded during thesol-gel transition. Once the solid gel structure has been formed, theexternal shape can only be changed by size reduction, for example, bypulverizing. The material is too brittle for any other form of stress.

[0006] For many applications, however, it is necessary to use theaerogel in certain shapes. In principle, the production of moulded partsis possible even as the gel is being formed. However, the replacement ofsolvents that is governed by diffusion (with respect to aerogels, see,for example, U.S. Pat. No. 4,610,863 and EP-A 0 396 0761; with respectto aerogel composite materials, see, for example, WO 93/06044), and thedrying--which is similarly governed by diffusion—lead to productiontimes that are economically unacceptable. For this reason, it isappropriate to carry out a shaping stage after the production of theaerogel, which is to say, after it has been dried, and to do thiswithout any essential change of the internal structure of the aerogeltaking place with respect to the particular application.

[0007] For many applications, however, it in addition to good thermalinsulation, an insulating material is also required to provide goodinsulation against airborne sound. Typically, good acoustic insulationis found in porous materials, the porosity of which lies on amacroscopic scale (greater than 0.1 μm) for then the velocity waves ofthe sound are attenuated by friction of the air on the walls of thepores. For this reason, monolithic materials without any macroscopicporosity display only a very low level of acoustic damping. If amaterial is only porous on a microscopic scale, as is the case withmonolithic aerogels, the air cannot flow through the pores; rather, thesound waves are transmitted on to the structure of the material and thisthen conducts them with out any marked attenuation.

[0008] DE-A 33 46 180 describes rigid panels from moulded bodies basedon silicic acid aerogel obtained by flame pyrolysis combined withreinforcement by long mineral fibres. However, this silicic acid aerogelthat is extracted from flame pyrolysis is not an aerogel in the abovesense since it is not manufactured by drying a gel, and for this reasonit has a completely different pore structure. Mechanically, it is muchmore stable and for this reason can be pressed without out destructionof the microstructure, although it has a greater thermal conductivitythan typical aerogels in the above sense. The surface of a moulded bodysuch as this is extremely delicate and for this reason must be hardened,as by the use of a binder, or by being covered with a film.

[0009] EP-A-O 340 707 describes an insulating material with a densityfrom 0.1 to 0.4 g/cm3 that consists of at least 50%-vol silica aerogelparticles with a diameter between 0.5 and 5 mm, that are connected bymeans of at least one organic and/or inorganic binder. If the aerogelparticles are connected by the binder only on the contact surfaces, theinsulating material that results is not very stable in the mechanicalsense since, under mechanical stress, the part of the aerogel particlethat is covered with the binder tears off, so that the particle is nolonger connected and the insulating material becomes cracked. For thisreason, as nearly as possible all the gaps between the aerogel particlesshould be filled with the binder. In the case of very small proportionsof binder, the resulting material is as stable as pure aerogels althoughcracks can occur very easily if all the grains of the granulate are notsufficiently enclosed by the binder.

[0010] In the case of a high volumetric percentage of binder that isfavourable for achieving a low degree of thermal conductivity, only verysmall proportions of the binder will remain in the spaces between theparticles and, especially in the case of porous binders such as foamswith lower thermal conductivity, this will result in low mechanicalstability. In addition, because of reduced macroscopic porosity (betweenthe particles), filling all the intervening spaces with binder causesmarkedly reduced acoustic damping within the material.

[0011] EP-A-489 319 describes a composite foam with a low level ofthermal conductivity, which contains 20 to 80%-vol of silica aerogelparticles, 20 to 80%-vol of a styrene polymer foam with a density of0.01 to 0.15 g/cm3 that encloses the aerogel particles and connects themto each other, and, if necessary, effective quantities of the usualadditives. The composite foam that is produced in this way is resistantto compression but is not very rigid at high concentrations of aerogelparticles.

[0012] German patent applications DE-A 44 30 669 and DE-A-44 30 642describe panels or mats of a fibre-reinforced aerogel. Is it is truethat, because of the very high proportion of aerogel, these panels ormats display a very low level of thermal conductivity, but they requirerelatively protracted production times because of the above-describeddiffusion problems.

[0013] The as-yet unpublished German patent application P 44 45 771.5describes a non-woven fibre textile-aerogel composite material that hasat least one layer of non-woven fibre textile and aerogel particles, andis characterised in that the non-woven fibre textile contains at leastone binary fibre material, the fibres of which are connected to eachother and to the aerogel particles by the low melting-point coveringmaterial. This composite material has a relatively low level of thermalconductivity and a high level of macroscopic porosity and, because ofthis, good acoustic damping, although the temperature range in which thematerial can be used, and its fire rating, are restricted by the use ofbinary fibres. In addition, the corresponding composite materials, inparticular complex moulded bodies, are not simple to manufacture.

[0014] For this reason, one of the tasks of the present invention was toproduce a composite material that is based on aerogel granulate, thathas a lower level of thermal conductivity, and is both mechanicallystable and easy to manufacture.

[0015] A further task of the present intention was to produce acomposite material that is based on aerogel granulate, and thatadditionally displays good acoustic damping characteristics.

[0016] This task is solved by a composite material that contains 5 to97%-vol aeroget particles, at least one binder, and at least one fibrematerial, the diameter of the aerogel particles being ≧0.5 mm.

[0017] The fibres or aerogels are either connected to each other andwith each other by the binder, or the binder serves as a matrix materialin which the fibres and the aerogel particles are embedded. Connectionof the fibres and the aerogel particles to each other and with eachother by the binder and, optionally, including them in a binder matrix,results in a mechanically stable material of very low thermalconductivity.

[0018] In contrast to a material that consists solely of aerogelparticles that are connected by their surfaces or embedded in a matrixof adhesive, most surprisingly, even small proportions of fibres byvolume can result in significant mechanical strengthening, given anequal proportion of binder by volume, since they assume large part ofthe load. If a greater volume of fibres is used with only a small amountof binder, it is possible to obtain a porous material in which thefibres that are connected by the binder form a mechanically stablestructure within which the aerogel particles are embedded. The air poresthat then result lead to a higher level of porosity, and thus toimproved acoustic damping.

[0019] Natural fibres such as cellulose, cotton, or flax fibres, as wellas synthetic fibres, can be used as the fibre material; with respect tosynthetic fibres, it is possible to use inorganic fibres such as glassfibres, mineral fibres, silicon carbide fibres or carbon fibres; and touse polyester fibres, polyamide fibres, or polyaramid fibres as organicfibres. The fibres can be new, or waste material such as shreddedglass-fibre waste or waste rags.

[0020] The fibres can be straight or crimped, and be in the form ofindividual fibres, wadding, or a non-woven or woven fibre material.Non-woven fibre material and/or textiles can be contained in the binderin the form of a cohesive whole and/or in the form of a number ofsmaller pieces.

[0021] The fibres can be round, trilobal, pentalobal, octalobal, in theform of strips, or be shaped like fir trees, dumb bells, or otherwise.Hollow fibres can also be used.

[0022] The diameter of the fibres that are used in the compositematerial should preferably be smaller than the mean diameter of theaerogel particles, so that a high proportion of aerogel is bound intothe composite material. The selection of very fine fibres makes thecomposite material slightly flexible.

[0023] It is preferred that fibres with diameters that are between 0.1μm and 1 mm are used. Typically, in the case of fixed proportions offibres by volume, the use of smaller diameters results in compositematerials that are more resistant to breakage.

[0024] There are no restrictions on the lengths of the fibres.Preferably, however, the lengths of the fibres should be greater thanthe mean diameter of the aerogel particles, i.e., at least 0.5 mm.

[0025] In addition, mixtures of the above types can be used.

[0026] The stability and the thermal conductivity of the compositematerial increase as the proportion of fibres increases. The volumetricpercentage of the fibres should preferably by between 0.1 and 40%-vol,and in particular in the range between 0.1 and 15%-vol, depending on theapplication.

[0027] In order to enhance the way in which they bind into the matrix,the fibres can be coated with sizing or coupling agents, as is typicallydone in the case of glass fibres.

[0028] Suitable aerogels for the composition according to the presentinvention are those based on metallic oxides, which are suitable for thesol-gel technique (C. J. Brinker, G. W. Scherer, Sol-Gel Science. 1990,Chaps. 2 and 3), for example, Si or Al compounds or such as those basedon organic substances that are suitable for the sol-gel technique, suchas melamine-formaldehyde condensates (U.S. Pat. No. 5,086,085) orresorcinformaldehyde condensates (U.S. Pat. No. 4,873,218). They canalso be based on mixtures of the above-cited materials. It is preferredthat aerogels containing Si compounds, especially SiO₂ aerogels, and inparticular SiO₂ aerogels, be used.

[0029] The aerogel can contain IR opacifiers, such as soot, titaniumdioxide, iron oxide, or zirconium dioxide, as well as mixtures of these,in order to reduce the radiation contribution to thermal conductivity.

[0030] Furthermore, the thermal conductivity of the aerogels decreasesas porosity increases and density decreases; this applies down todensities in the vicinity of 0.1 g/cm³. For this reason, aerogels withporosities of greater than 60% and densities between 0.1 and 0.4 g/cm³are especially preferred. It is preferred that the thermal conductivityof the aerogel granulate be less than 40 mW/mK, and in particular lessthan 25 mW/mK.

[0031] In a preferred embodiment, hydrophobic aerogel particles areused; these can be obtained by incorporating hydrophobic surface groupson the pore surfaces of the aerogels during or after production of theaerogels.

[0032] In the present application, the term “aerogel particles” is usedto designate particles that are either monolithic, i.e., are composed ofone piece, or, essentially, aerogel particles with a diameter that issmaller than the diameter of the particles that are joined by a suitablebinder and/or compressed to form a larger particle. The size of thegrains will depend on the use to which the material is put. In order toachieve a higher level of stability, the granulate should not be toocoarse, and it is preferred that the diameter of the grains be smallerthan 1 cm and, in particular, smaller than 5 mm.

[0033] On the other hand, the diameter of the aerogel particles shouldbe greater than 0.5 mm in order to avoid the difficulties associatedwith handling a very fine powder of low density. In addition, as a rule,during processing, the liquid binder penetrates into the upper layers ofthe aerogel that, in this area, loses its great effectiveness asinsulation. For this reason, the proportion of macroscopic particlesurface to particle volume should be as small as possible, which wouldnot be the case were the particles too small.

[0034] In order to achieve low thermal conductivity, on the one handand, on the other, to achieve adequate mechanical stability of thecomposite material, the volumetric percentage of aerogel shouldpreferably by between 20 and 97%-vol, and especially between 40 and95%-vol, with greater volumetric percentages leading to lower thermalconductivity and strength. In order to achieve a high level of porosityof the overall material, and enhanced acoustic absorption, air poresshould be incorporated in the material, to which end the volumetricpercentage of aerogel should preferably be less than 85%-vol.

[0035] Granulate with a favourable bimodal grain size distribution canbe used to achieve a high volumetric percentage of aerogel. Otherdistributions could also be used, depending on the application, e.g., inthe area of acoustic damping.

[0036] The fibres or aerogel particles are connected to each other andthe fibres and aerogel particles are connected to each other by at leastone binder. The binder can either serve only to join the fibres andaerogel particles to each other and with each other, or can serve asmatrix material.

[0037] In principle, all known binders are suitable for manufacturingthe composite materials according to the present invention. Inorganicbinders such as water glass adhesive, or organic binders or mixturesthereof can be used. The binder can also contain additional inorganicand/or organic components.

[0038] Suitable organic binders are, for example, thermoplastics such aspolyolefins or polyolefin waxes, styrene polymers, polyamides,ethylenevinylacetate copolymers or blends thereof, or duroplasts such asphenol, resorcin, urea, or melamine resins. Adhesives such as fusionadhesives, dispersion adhesives (in aqueous form, e.g., styrenebutadiene, and styrene acryl ester copolymers), solvent adhesives orplastisols can also be used; also suitable are reaction adhesives, e.g.,in the form of unary systems such as heat-hardened epoxy resins,formaldehyde condensates, polyimides, polybenzimidazoles, cyanacrylates,polyvinylbutyrals, polyvinyl alcohols, anaerobic adhesives, polyurethaneadhesives, and moisture hardened silicones, or in the form of binarysystems such as methacrylates, cold-hardened epoxy resins, binarysilicones and cold-hardened polyurethanes.

[0039] It is preferred that polyvinylbutyrals and/or polyvinyl alcoholsbe used

[0040] It is preferred that the binder be so selected that if it is inliquid form during specific phases of the processing, within this timeframe it cannot penetrate into the very porous aerogel, or can do so toonly an insignificant extent. Penetration of the binder into theinterior of the aerogel particles can be controlled by the selection ofthe binder and by regulating processing conditions such as pressure,temperature, and mixing time.

[0041] If the binder forms a matrix in which the aerogels and fibres areembedded, then, because of their low thermal conductivity, porousmaterials with densities of less than 0.75 g/cm³, such as foams,preferably polymer foams (e.g., polystyrene or polyurethane foams) areused.

[0042] In order to achieve the good distribution of the binder in theinterstices when large proportions of aerogel are used, and in order toachieve good adhesion, in the event that a solid form of binder is used,the grains of the binder should preferably be smaller than those of theaerogel granulate. Processing at greater pressure may also be required.

[0043] If the binder has to be processed at elevated temperatures, as inthe case of fusion adhesives or reaction adhesives such as, for example,melamineformaldehyde resins, then the binder must be so selected thatits fusion temperature does not exceed the fusion temperature of thefibres.

[0044] In general, the binder is used at a rate of 1 to 50%-vol of thecomposite material, preferably at a rate of 1 to 30%-vol. The selectionof the binder will be governed by the mechanical and thermal demandsplaced on the composite material, as well as requirements with respectto fire protection.

[0045] The binder can also contain effective quantities of otheradditives such as, for example, colouring agents, pigments, extenders,fire retardant agents, synergists for fire protection agents,anti-static agents, stabilizers, softeners, and infra-red opacifiers.

[0046] In addition, the composite material can also contain additivesthat are used to manufacture it or which are formed when it ismanufactured; such substances can include slip agents for compression,such as zinc stearate, or the reaction products formed from acid oracid-cleaving hardening accelerators, when resins are used.

[0047] The fire rating of the composite material is determined by thefire ratings of the aerogel, the fibres, and the binder,and—optionally—by that of the other substances contained in it. In orderto arrive at the most favourable fire rating for the composite material,non-flammable fibres such as glass or mineral fibres, or fibres that aredifficult to ignite, such as TREVIRA CS®, or melamine resin fibres,aerogels based on inorganic substanes, preferably based on SiO₂, areused; also used are binders that are difficult to ignite, such asinorganic binders of urea and melamineformaldehyde resins, silicon resinadhesives, polyimide and polybenzimidazol resins.

[0048] If the material is used in the form of flat structures such aspanels or mats, these can be covered on at least one side with at leastone covering layer in order to improve its surface properties, and tomake it more robust, form it as a vapour barrier, or protect it againstsoiling. These covering layers can also enhance the mechanical stabilityof moulded parts made from the composite material. If covering layersare used on both sides, these can either be identical or different.

[0049] All materials known to the practitioner skilled in the art aresuitable for use as covering layers. They can be non-porous and therebyact as a vapour barrier, e.g., plastic films, preferably metal films, ormetallized plastic films that reflect thermal radiation. It is alsopossible to use porous covering layers such as porous films, papers,textiles, or non-woven fabrics that permit air to penetrate into thematerial and thereby enhance its acoustic damping properties.

[0050] The covering layers can themselves consist of a plurality oflayers. The covering layers can be secured with the binder that joinsthe fibres and the aerogel particles to each other and with each other,although another, different adhesive can also be used.

[0051] The surface of the composite material can be also be sealed andconsolidated by incorporating at least one suitable material into asurface layer.

[0052] Suitable materials are thermoplastic polymers such aspolyethylene and polypropylene, or resins such as melamineformaldehyderesins.

[0053] It is preferred that the composite materials according to thepresent invention have a thermal conductivity that is between 10 and 100mW/mK, especially in the range from 10 to 50 mW/mK, and in particular inthe range from 15 to 40 mW/mK.

[0054] A further task of the present invention was to provide for aprocess to manufacture the composite materials according to the presentinvention.

[0055] If the binder is initially in the form of a powder that fuses atan elevated temperature and, if necessary, at an elevated pressure andthen reacts, as in the case of reaction adhesives, then the compositematerial can be obtained as follows: aerogel particles, fibre material,and the binder are mixed using conventional mixers. The mixture is thensubjected to a shaping process. The mixture will be hardened in themould by heating, if necessary under pressure, depending on the type ofbinder, e.g., in the case of reaction adhesives, or in the case offusion adhesives by being heated to a point above the melting point ofthe binder. A material that is porous on a macro scale can be obtained,in particular, according to the following procedure: in the event thatthe fibres are not already in the form of wadding (e.g., small tufts ofcut fibres or small pieces of a film) it will be processed to form smalltufts by methods familiar to the practitioner skilled in the art. Evenin this step it is, if necessary, possible to incorporate the aerogelgranulate between the fibres. Subsequently, these tufts together withthe binder and, optionally, the aerogel particles, are mixed, forexample in a mixer, until such time as the binder and, optionally, theaerogel particles are distributed as evenly as possible between thefibres. The compound is then placed in a mould and, if necessary underpressure, heated to a temperature that, in the case of fusion adhesives,is above the fusion temperature of the adhesive and, in the case ofreaction adhesives, is above the temperature that is required for thereaction. Once the binder has fused or has reacted, the material iscooled. It is preferred that polyvinylbutyrals are used here. Thedensity of the composite material can be increased by using a higherpressure.

[0056] In one preferred embodiment, the mixture is compressed. When thisis done, the practitioner skilled in the art can select the press andthe pressing die that are best suited for the particular application. Ifnecessary, the practitioner can add known slip agents such as zincstearate to the pressing process when melamineformaldehyde resins areused. The use of vacuum presses is particularly advantageous because ofthe large amount of air in the moulding compound that contains aerogels.In a preferred embodiment, the moulding compound that contains theaerogel is compressed to form panels. In order to avoid the compoundbaking onto the pressure ram, the mixture that contains the aerogel andwhich is to be compressed can be separated from the pressure ram byrelease paper. The mechanical strength of the panels that contain theaerogel can be enhanced by laminating mesh fabrics, non-woven fabrics,or papers onto the surface of the panel. These mesh textiles, non-wovenfabrics, or papers can be applied to the panels that contain aerogelsubsequently, in which case the mesh fabrics, non-woven textiles, orpapers are previously impregnated with suitable binder or adhesive, andthen bonded to the surface of the panel in a heated press when underpressure. In addition, in one preferred embodiment, this can be done inone step by laying up the mesh textiles, non-woven textiles, and paper,optionally previously impregnated with a suitable binder or adhesive, inthe press mould and applying them to the moulding compound that containsthe aerogel and which is to be pressed, and then subjecting them topressure and elevated temperatures to form a composite panel thatcontains aerogels.

[0057] Depending on the binder that is used, in any moulds, the pressinggenerally takes place at pressures from 1 to 1000 bar and attemperatures from 0 to 300° C.

[0058] In the case of phenol, resorcin, urea, and melamineformaldehyderesins, pressing preferably takes place at pressures from 5 to 50 bar,especially at 10 to 20 bar, and at temperatures preferably from 100 to200° C., especially from 130 to 190° C., and in particular between 150and 175° C.

[0059] If the binders is initially in liquid form, the compositematerial can be obtained in the following way: the aerogel particles andthe fibre material are mixed using conventional mixers. The mixture soobtained is then coated with the binder, for example, by spraying,placed in a mould, and then hardened in this mould. Depending on thetype of binder that is used, the mixture is hardened under pressure byheating and/or by evaporating off the solvent or dispersant that isused. It is preferred that the aerogel particles be swirled with thefibres in a flow of gas. A mould is then filled with the mixture, withthe binder being sprayed on during the filling process. A material thatis porous on a macro scale can be obtained in the following way: in theevent that the fibres are not already in bulked form (e.g., small tuftsof cut fibre or small pieces of a non-woven fabric), they are processedinto small tufts using methods that are familiar to the practitionerskilled in the art. Even in this step the aerogel granulate can, ifnecessary, be incorporated between the fibres. Otherwise, these tuftsare mixed with the aerogel granulate in a mixer until the aerogelparticles have been distributed as evenly as possible between thefibres. In this step, or subsequently, the binder is sprayed, divided asfinely as possible, onto the mixture and the mixture is then placed in amould and heated—if necessary under pressure—to the temperature that isrequired for bonding. Subsequently, the composite material is driedusing a conventional process.

[0060] If a foam is used as binder, the composite material can beproduced as follows, depending on the type of foam that is used.

[0061] If the foam is manufactured in a mould by the expansion ofexpandable granulate grains, as in the case of expanded polystyrene, allthe components can be thoroughly mixed and then typically heated,advantageously by means of hot air or steam. Because of the expansion ofthe particles, the pressure in the mould increases, which means that theinterstices are filled with foam and the aerogel particles are fixed inthe composite. After cooling, the moulded part of composite material isremoved from the mould and dried, should this be necessary.

[0062] If the foam is manufactured by extrusion or expansion of anon-viscous mixture, with subsequent solidification, the fibres can bemixed into the liquid. The aerogel particles are mixed into theresulting liquid, which then foams.

[0063] If the material is to be provided with a covering layer, this canthen be laid up in a mould, prior to or after the filling process, sothat coating and shaping can take place in one step, with the binderused for the composite material also being used as binder for thecoating. However, it is also possible to provide the composite materialwith a covering layer in a subsequent step.

[0064] The shape of the moulded part that consists of the compositematerial according to the present invention is in no way restricted; inparticular, the composite material can be formed into panels.

[0065] Because of the high percentage of aerogel and their low thermalconductivity, the composite materials are particularly well suited asthermal insulation.

[0066] Formed into panels, the composite material can be used as soundabsorbing material, either directly in or in the form of resonanceabsorbers for acoustic insulation. In addition to the damping of theaerogel material, depending on the porosity that results frommacroscopic pores, additional damping is provided as a result of airfriction on these macroscopic pores in the composite material. Themacroscopic porosity can be regulated by changing the proportion offibres and their diameter, the grain size and proportion of aerogelparticles, and the type of binder. The frequency function of acousticdamping and its degree can be changed by selection of the coveringlayer, the thickness of the panel, and its macroscopic porosity, whichis done in a manner known to the practitioner skilled in the art.

[0067] Because of its macroscopic porosity and, in particular, its greatporosity, and the specific surface of the aerogel, the compositematerials according to the present invention are also suitable asadsorption materials for liquid, vapours, and gasses.

[0068] The present invention will be described in greater detail belowon the basis of exemplary embodiments without, however, being restrictedto these:

EXAMPLE 1

[0069] Moulded part of aerogel, polyvinylbutyral, and fibres 90%-volhydrophobic aerogel granulate, 8%-vol Mowital® (Polymer F)polyvinylbutyral powder and 2%-vol Trevira® high-strength fibres arethoroughly mixed.

[0070] The hydrophobic aerogel granulate has an average grain size inthe range from 1 to 2 mm, a density of 120 kg/m³, a BET surface of 620m²/g and a thermal conductivity of 11 mW/mK.

[0071] The bottom of the press mould, with a base area of 30 cm×30 cm,is covered with release paper. The moulding material that contains theaerogel is applied evenly to this, and the whole is then covered withrelease paper, after which it is pressed to a thickness of 18 mm at 220°C. for a period of 30 minutes.

[0072] The moulded part obtained in this way has a density of 269 kg/m³and a thermal conductivity of 20 mW/mK.

EXAMPLE 2

[0073] Moulded part of aerogel, polyvinylbutyral, and recycling fibres80%-vol hydrophobic aerogel granulate as described in Example 1, 10%-volMowital® (Polymer F) polyvinylbutyral powder and 10%-vol of coarselyshredded polyester fibre remnants as the recycling fibres are thoroughlymixed.

[0074] The bottom of the press mould, with a base area of 30 cm×30 cm,is covered with release paper. The moulding material that contains theaerogel is applied evenly to this, and the whole is then covered withrelease paper, after which it is pressed to a thickness of 18 mm at 220°C. for a period of 30 minutes.

[0075] The moulded part obtained in this way has a density of 282 kg/m³and a thermal conductivity of 25 mW/mK.

EXAMPLE 3

[0076] Moulded part of aerogel, polyvinylbutyral, and recycling fibres50%-vol hydrophobic aerogel granulate as described in Example 1, 10%-volMowital® (Polymer F) polyvinylbutyral powder and 40%-vol of coarselyshredded polyester fibre remnants as the recycling fibres are thoroughlymixed.

[0077] The bottom of the press mould, with a base area of 30 cm×30 cm,is covered with release paper. The moulding material that contains theaerogel is applied evenly to this, and the whole is then covered withrelease paper, after which it is pressed to a thickness of 18 mm at 220°C. for a period of 30 minutes.

[0078] The moulded part obtained in this way has a density of 420 kg/m³and a thermal conductivity of 55 mW/mK.

EXAMPLE 4

[0079] Moulded part of aerogel, polyethylene wax, and fibres 60%-wt ofhydrophobic aerogel granulate as described in Example 1, and 38%-wtCeridust® 130 polyethylene wax powder, and 2%-vol Trevira® high strengthfibres are thoroughly mixed.

[0080] The bottom of the press mould, with a base area of 12 cm×12 cm,is covered with release paper The moulding material, which contains theaerogel, is applied evenly to this, and the whole is then covered withrelease paper. A pressure of 70 bar is applied at 170° C. for 30minutes.

[0081] The moulded part obtained in this way has a thermal conductivityof 25 mW/mK

EXAMPLE 5

[0082] Moulded part of aerogel, polyethylene wax, and fibres 50%-wt ofhydrophobic aerogel granulate as described in Example 1, and 48%-wtHoechst-Wachs PE 520 polyethylene wax powder, and 2%-vol Trevira® highstrength fibres are thoroughly mixed.

[0083] The bottom of the press mould, with a base area of 12 cm×12 cm,is covered with release paper The moulding material, which contains theaerogel, is applied evenly to this, and the whole is then covered withrelease paper. A pressure of 70 bar is applied at 180° C. for 30minutes.

[0084] The moulded part obtained in this way has a thermal conductivityof 28 mW/mK

EXAMPLE 6

[0085] Moulded part of aerogel, polyvinylalcohol, and fibres 90%-wt ofthe hydrophobic aerogel granulate as described in Example 1, 8%-wt of apolyvinylalcohol solution, and 2%-vol Trevira® high strength fibres arethoroughly mixed. The polyvinylalcohol solution consists of 10%-wt Type40-88 Mowiol®, 45%-wt water, and 45%-wt ethanol.

[0086] The bottom of the press mould, with a base area of 12 cm×12 cm,is covered with release paper. The moulding material that contains theaerogel is applied evenly to this, and the whole is then covered withrelease paper, after which it is pressed at a pressure of 70 bar for aperiod of 2 minutes, and then dried

[0087] The moulded part obtained in this way has a thermal conductivityof 24 mW/mK.

[0088] The thermal conductivity of the aerogel granulates was measuredby a hot-wire method (see, for example, O. Nielsson, G. Rüschenpöhler,J. Groβ, J. Fricke, High Temperatures-High Pressures, Vol. 21, pp.267-274 (1989)). The thermal conductivity of the moulded parts wasestablished in accordance with DIN 52612.

1. Composite material containing 5 to 97%-vol of aerogel particles, atleast one binder, and at least one fibre material, the diameter of theaerogel particles being ≧0.5 mm.
 2. Composite material as defined inclaim 1, characterized in that the percentage volume of fibre materialis 0.1 to 40%-vol.
 3. Composite material as defined in claim 1 or claim2, characterised in that the fibre material contains glass fibres as theprincipal component.
 4. Composite material as defined in claim 1 orclaim 2, characterised in that the fibre material contains organicfibres as the principal component.
 5. Composite material as defined inat least one of the claims 1 to 4, characterised in that the proportionof aerogel particles is in the range from 20 to 97%-vol.
 6. Compositematerial as defined in at least one of the claims 1 to 5, characterisedin that the porosity of the aerogel particles is greater than 60%, theirdensity is lower than 0.4 g/cm3, and their thermal conductivity is lessthan 40 mW/mK.
 7. Composite material as defined in at least one of theclaims 1 to 6, characterised in that the aerogel is an SiO₂ aerogel thathas if necessary been organically modified.
 8. Composite material asdefined in at least one of the claims 1 to 7, characterised in that atleast some of the aerogel particles have hydrophobic surface groups. 9.Composite material as defined in at least one of the claims 1 to 8,characterised in that the binding agent is of a density that is smallerthan 0.75 g/cm3.
 10. Composite material as defined in at least-one ofthe claims 1 to 9, characterised in that the binder contains aninorganic binder as the principal component.
 11. Composite material asdefined in claim 10, characterised in that the inorganic binder is waterglass.
 12. Composite material as defined in at least one of the claims 1to 9, characterised in that the binder contains an organic binder as theprincipal component.
 13. Composite material as defined in claim 12,characterised in that the organic binder is polyvinylbutyral and/orpolyvinylalcohol.
 14. Composite material as defined in at least one ofthe claims 1 to 13, characterised in that at least some of the aerogelparticles and/or the binder contain at least one infra-red opacifier.15. Composite material as defined in at least one of the claims 1 to 14,characterised in that it is of a flat shape and is covered on at leastone side with at least one covering layer.
 16. A process formanufacturing a composite material as defined in at least one of theclaims 1 to 15, characterised in that the aerogel particles and thefibre materials are mixed with the binder, and the mixture is subjectedto shaping and hardening.
 17. Use of a composite material as defined inat least one of the claims 1 to 15 for thermal and/or acousticinsulation.
 18. Moulded part containing a composite material as definedin at least one of the claims 1 to
 15. 19. Moulded part, consistingessentially of a composite material as defined in at least one of theclaims 1 to
 15. 20. Moulded partner defined in claim 18 or claim 19,characterised in it is in the form of a panel.